η′\eta^\prime photoproduction near threshold

In this work, the $\eta^\prime$ meson photoproduction near threshold is studied in the quark model framework. A pseudovector effective Lagrangian is introduced for the $\eta^\prime NN$ coupling and the newly published data from the SAPHIR Collaboration provide good constraints to this parameter. Corrections of order $O(1/m_q^2)$ for the electromagnetic interaction vertex are taken into account, which produce corrections of order $O(1/m_q^3)$ to the transition amplitude for $\gamma p\to \eta^\prime p$. Some low-lying resonances, $S_{11}(1535)$, $P_{13}(1720)$, and $P_{13}(1900)$ are found to have significant contributions. A bump structure around $E_\gamma\approx$ 2 GeV is found arising from the $n=3$ terms in the harmonic oscillator basis. The beam polarization asymmetries are predicted and can be tested against the forthcoming data from GRAAL.Comment: Revtex, 3 eps figures, 1 table; Resubmitted to Phys. Rev.

Quark model approach to the η\eta meson electroproduction on the proton

A recently developed quark model approach to pseudoscalar meson photoproduction is extended to electroproduction process for the $\eta$ meson in the kinematics of momentum transfer $Q^2 \leq$ 4 (GeV/c)$^2$ and total center of mass energy $W \leq$ 1.6 GeV. Existing data are well reproduced and the roles of the $S_{11}(1535)$ and $D_{13}(1520)$ resonances are closely investigated. In the study of the longitudinal excitation of the $S_{11}(1535)$ resonance, a reliable constraint on the $S_{11}(1535)$ properties is obtained by cleanly removing the electromagnetic transition from the $\gamma_{(v)} p \to S_{11}(1535) \to \eta p$ amplitude. Thus, the fitted quantities can be determined with an uncertainty of about 15%. This could be the first direct constraint on the $S_{11}(1535)$ properties in theory.Comment: 31 pages, 9 figures; Substantially modified version, to appear on Jour. of Phys.